Liquid crystal display device

ABSTRACT

A liquid crystal display device according to an aspect of the present invention includes a first substrate including a pixel electrode and a common electrode, a second substrate opposed to the first substrate, and a liquid crystal layer disposed between the first substrate and the second substrate. The pixel or common electrode includes, in a single subpixel, belt-like portions arranged in a first direction, and coupling portions coupling the adjacent belt-like portions. Each belt-like portion continuously extends from one side to an other side of a central line of the subpixel, that is parallel with the first direction. The coupling portions include one or more first coupling portions provided on the one side of the central line, and one or more second coupling portions provided on the other side of the central line.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Japanese Application No.2015-208344, filed on Oct. 22, 2015, the contents of which areincorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a liquid crystal display device.

2. Description of the Related Art

A liquid crystal display device disclosed in Japanese Patent ApplicationLaid-open Publication No. 2014-209212 (JP-A-2014-209212) is known as aliquid crystal display device of a transverse electric field type inwhich pixel electrodes and a common electrode are provided on the samesubstrate. The liquid crystal display device disclosed inJP-A-2014-209212 is a liquid crystal display device in which a pluralityof slits are formed in the common electrode, and the common electrode isdisposed on a liquid crystal layer side of the pixel electrodes.

In the liquid crystal display device disclosed in JP-A-2014-209212,adjacent slits communicate with each other through a communicatingportion. With the structure, when a voltage is applied between the pixelelectrode and the common electrode, liquid molecules in the vicinity oftwo sides opposite to each other in the same slit are rotated indirections opposite to each other. This structure achieves high-speedresponse. However, because this structure forms a region in whichorientation of liquid crystal molecules hardly changes, in the centralportions of the slits and in a position on an electrode disposed betweenslits, display may be darkened.

SUMMARY

A liquid crystal display device according to an aspect of the presentinvention includes: a first substrate including a pixel electrode and acommon electrode; a second substrate disposed opposite to the firstsubstrate; and a liquid crystal layer disposed between the firstsubstrate and the second substrate. The pixel electrode or the commonelectrode includes, in a single subpixel, a plurality of belt-likeportions arranged in a first direction, and a plurality of couplingportions that are configured to couple adjacent belt-like portions ofthe plurality of belt-like portions. Each of the plurality of belt-likeportions continuously extends from one side to an other side of acentral line of the single subpixel. The central line is parallel withthe first direction and disposed between the one side and the otherside. The plurality of coupling portions include one or more firstcoupling portions provided on the one side of the central line and oneor more second coupling portions provided on the other side of thecentral line.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a liquid crystal display deviceaccording to a first embodiment;

FIG. 2 is an equivalent circuit schematic of a display region;

FIG. 3 is a plan view of a pixel as viewed from a normal direction of afirst substrate;

FIG. 4 is a plan view illustrating an electrode structure of a subpixel;

FIG. 5 is a cross-sectional view taken along line A1-A2 in FIG. 3;

FIG. 6 is an enlarged plan view of a part of the electrode structureillustrated in FIG. 5;

FIG. 7 is a diagram illustrating an orientation state of liquidmolecules when a voltage is applied;

FIG. 8 is a plan view illustrating a transmission light image of asubpixel SPX when a voltage is applied;

FIG. 9 is a plan view illustrating an electrode structure of a liquidcrystal display device according to a second embodiment;

FIG. 10 is a plan view illustrating an electrode structure of a liquidcrystal display device according to a third embodiment;

FIG. 11 is a plan view illustrating an electrode structure of a liquidcrystal display device according to a fourth embodiment; and

FIG. 12 is a plan view illustrating an electrode structure of a liquidcrystal display device according to a fifth embodiment.

DETAILED DESCRIPTION

Modes (embodiments) for carrying out the invention will be explainedhereinafter in detail with reference to drawings. The present inventionis not limited by the details described in the following embodiments. Inaddition, the constituent elements described hereinafter includeelements that the skilled person could easily think of, andsubstantially the same elements. The constituent elements describedhereinafter can be properly combined. The disclosure is a mere example,and the scope of the present invention includes proper modificationsthat the skilled person could easily think of with the gist of theinvention maintained, as a matter of course. The drawings may moreschematically illustrate the widths, thicknesses, and shapes of themembers than the actual mode to further clarify the explanation, butprovide a mere example, and do not limit the interpretation of thepresent invention. In the specification and the drawings, like elementsas those illustrated in the foregoing drawings may be denoted by likereference numerals, and detailed explanation thereof may be properlyomitted.

First Embodiment

FIG. 1 is a block diagram illustrating a liquid crystal display device100 according to a first embodiment. In the following explanation, anXYZ coordinate system is used to explain the positional relation of themembers and the like.

The liquid crystal display device 100 includes a liquid crystal panel110 and a drive IC 120. The liquid crystal panel 110 includes a firstsubstrate 130 and a second substrate 150 that are disposed opposite toeach other with a liquid crystal layer interposed therebetween. Thefirst substrate 130 is formed larger than the second substrate 150, anda portion of the first substrate 130 projecting outside the secondsubstrate 150 serves as a terminal portion. The drive IC 120 is providedin the terminal portion.

A display region 110A is provided in a central portion of a oppositeregion in which the first substrate 130 is opposite to the secondsubstrate 150. The display region 110A is provided with a plurality ofgate lines 113 extending in an X direction and a plurality of sourcelines 114 extending in a Y direction such that the gate lines 113 andthe source lines 114 cross each other. The gate lines 113 are arrangedside by side in the Y direction, and the source lines 114 are arrangedside by side in the X direction.

Subpixels SPX are provided to correspond to respective crossing portionsbetween the gate lines 113 and the source lines 114. The subpixels SPXare arranged along the extending direction of the gate lines 113 and theextending direction of the source lines 114 and side by side in the Xdirection and the Y direction. The display region 110A is formed byarranging the subpixels SPX in the X direction and the Y direction. Theshape of the display region 110A is, for example, a rectangular shape,but the shape of the display region 110A is not limited to a rectangularshape. For example, the display region 110A may have any shape otherthan a rectangular shape, such as a polygonal shape, a circular shape,and an oval shape.

A gate driver 111 and a source driver 112 are provided in a peripheralportion of the opposite region. The gate driver 111 is provided along afirst side of the display region 110A. The source driver 112 is providedalong a second side of the display region 110A. Each of the gate lines113 is electrically coupled with the gate driver 111. Each of the sourcelines 114 is electrically coupled with the source driver 112. The gatedriver 111 and the source driver 112 are electrically coupled with thedrive IC 120. The gate driver 111 and the source driver 112 are, forexample, provided separately along two sides of the display region 110Athat are mutually orthogonal, but arrangement of the gate driver 111 andthe source driver 112 is not limited thereto. For example, the gatedriver 111 and the source driver 112 may be provided along the same sideof the display region 110A.

FIG. 2 is an equivalent circuit schematic of the display region 110A.

The subpixels SPX are provided with respective pixel electrodes 141.Each of the pixel electrodes 141 is electrically coupled with athin-film transistor 116. A source of a thin-film transistor 116 iselectrically coupled with a source line 114. An image signal is suppliedto each of the subpixels SPX through the source lines 114. An imagesignal may be supplied to the source lines 114 in a line sequentialmanner. As another example, adjacent source lines 114 may be grouped,and an image signal may be supplied to each of the groups.

A gate of a thin-film transistor 116 is electrically coupled with a gateline 113. A gate signal is supplied to the gate lines 113 in a linesequential manner. Each pixel electrode 141 is electrically coupled witha drain of a thin-film transistor 116. A common electrode 139 iselectrically coupled with common lines 115. When a thin-film transistor116 is turned on for a certain period by input of a gate signal, animage signal supplied from the source line 114 is written to the pixelelectrode 141. The image signal written to the pixel electrode 141 isheld for a certain period between the pixel electrode 141 and the commonelectrode 139. A liquid crystal layer 160 has orientation changingaccording to an electric field generated between the pixel electrode 141and the common electrode 139. In this manner, light made incident on theliquid crystal layer 160 is modulated to perform gradation display.

The display region 110A is provided with a plurality of types ofsubpixels SPX displaying mutually different colors. The color displayedby one subpixel SPX is determined according to the color of a colorfilter CF thereof. For example, the example of FIG. 2 has a structure inwhich a first subpixel SPX1 including a color filter CF1 of a firstcolor, a second subpixel SPX2 including a color filter CF2 of a secondcolor, and a third subpixel SPX3 including a color filter CF3 of a thirdcolor are provided to be mutually adjacent. One subpixel SPX is a region(region surrounded by a black matrix BM) in which display is performedby one pixel electrode 141 and the common electrode 139. One pixel PX isformed of a plurality of types of adjacent pixels SPX (the firstsubpixel SPX1, the second subpixel SPX2, and the third subpixel SPX3).Full-color display is performed by controlling gradation of each of thesubpixels SPX of a plurality of types provided in each pixel PX. In thedisplay region 110A, a plurality of pixels PX are arranged side by sidein the X direction and the Y direction.

FIG. 3 is a plan view of a pixel PX as viewed from a normal direction (Zdirection) of the first substrate 130. FIG. 4 is a plan viewillustrating an electrode structure of a subpixel SPX.

As illustrated in FIG. 3, each of three subpixels SPX forming a pixel PXis provided with a pixel electrode 141 and the common electrode 139. Thecommon electrode 139 is partly superimposed on the pixel electrode 141with an insulating film interposed therebetween. The pixel electrode 141or the common electrode 139 includes, in one subpixel SPX, a pluralityof belt-like portions 142 arranged in the Y direction (first direction),and a plurality of coupling portions 143 coupling the adjacent belt-likeportions 142.

In the present embodiment, for example, the pixel electrode 141 isdisposed on the liquid crystal layer side of the common electrode 139with the insulating film interposed between the pixel electrode and thecommon electrode, and the pixel electrode 141 is provided with theplurality of belt-like portions 142 and the plurality of couplingportions 143. The belt-like portions 142 and the coupling portions 143are formed by providing a plurality of slits SL in the pixel electrode141. Two adjacent belt-like portions 142 are opposite to each other witha slit SL interposed therebetween. For example, only one couplingportion 143 is disposed between two adjacent belt-like portions 142, andthe two belt-like portions 142 are electrically and mechanically coupledwith the coupling portion 143.

As illustrated in FIG. 4, each of the plurality of belt-like portions142 extends continuously from one side (for example, +X side) to another side (for example, −X side) of a central line CL of the subpixelSPX. The central line CL is parallel with the Y direction (firstdirection), and is disposed between the sides. The plurality of couplingportions 143 include one or more first coupling portions 143 a providedon one side of the central line CL and one or more second couplingportions 143 b provided on the other side of the central line CL.

In the present embodiment, for example, the first coupling portions 143a and the second coupling portions 143 b are alternately arrangedrepeatedly in the Y direction (first direction). Among the belt-likeportions 142 provided in one subpixel SPX, at least some belt-likeportions 142 (for example, a plurality of belt-like portions 142 otherthan one or a plurality of belt-like portions 142 provided in endportions) provided in the central portion has a length equal to eachother. The belt-like portions 142 provided in the central portion arearranged side by side in the Y direction at uniform pitch.

Each pixel electrode 141 has a widened portion 144 having a larger widthin the Y direction than that of the belt-like portions 142, on one endside (for example, +Y side) in the arrangement direction of thebelt-like portions 142. The widened portion 144 is electrically coupledwith the belt-like portion 142 that is disposed closest to the end. Ablack matrix BM is provided around each pixel electrode 141. The blackmatrix BM is a light shield layer having an opening portion OBM in aposition opposite to the central portion of the pixel electrode 141. Theregion provided with the opening portion OBM serves as the subpixel SPX.The black matrix BM is disposed to be superimposed on part or whole ofthe widened portion 144. The belt-like portions 142 and the couplingportions 143 are disposed in the opening portion OBM.

The common electrode 139 is provided in a position in which the commonelectrode 139 is superimposed on at least a space between the adjacentbelt-like portions 142. The common electrode 139 is, for example, formedon the whole surface of the display region, but the shape of the commonelectrode 139 is not limited thereto. For example, the common electrode139 may be divided into a plurality of portions in the display region,and the divided individual portions may be electrically coupled with thecommon lines 115 (see FIG. 2).

With reference to FIG. 3 again, the display region 110A is provided withthe gate lines 113 extending in the X direction and the source lines 114extending in the Y direction along spaces between the pixel electrodes141. The thin-film transistors 116 are provided in the vicinity of therespective crossing portions between the gate lines 113 and the sourcelines 114. Each thin-film transistor 116 includes a gate electrode 132,a semiconductor layer 134, a source electrode 135, and a drain electrode136.

The gate electrode 132 is provided to branch from the gate line 113 inthe Y direction. The semiconductor layer 134 is provided to besuperimposed on the gate electrode 132. The source electrode 135 isprovided to branch from the source line 114 in the X direction, andincludes an end portion on the +X side electrically coupled with thesource portion of the semiconductor layer 134. The drain electrode 136is provided opposite to the source electrode 135 in the X direction witha channel portion of the semiconductor layer 134 interposedtherebetween. The widened portion 144 of the pixel electrode 141 isprovided along the gate line 113, and includes an end portion on the −Xside electrically coupled with the drain electrode 136.

FIG. 5 is a cross-sectional view taken along line A1-A2 of FIG. 3.

The liquid crystal display device 100 includes the first substrate 130including the pixel electrodes 141 and the common electrode 139, thesecond substrate 150 disposed opposite to the first substrate 130, andthe liquid crystal layer 160 disposed between the first substrate 130and the second substrate 150.

The first substrate 130 includes a first base material 131 formed of atranslucent insulating member such as glass. The gate lines 113 and thegate electrode 132 are formed on the internal surface side (liquidcrystal layer 160 side) of the first base material 131. A gateinsulating film 133 formed of a translucent insulating member such assilicon oxide is formed on the first base material 131, to cover thegate lines 113 and the gate electrode 132. The semiconductor layer 134formed of amorphous silicon, low-temperature polycrystalline silicon(LTPS), or a semiconductor oxide is formed on the gate insulating film133. The source electrode 135 and the drain electrode 136 are formed onthe gate insulating film 133, to be partly placed on the semiconductorlayer 134.

A first interlayer insulating film 137 formed of a translucentinsulating member such as silicon oxide is formed on the gate insulatingfilm 133, to cover the semiconductor layer 134, the source electrode135, and the drain electrode 136. A second interlayer insulating film138 formed of a translucent insulating member such as acrylic resin isformed on the first interlayer insulating film 137. The common electrode139 formed of a translucent conductive member such as indium tin oxide(ITO) is formed on the second interlayer insulating film 138. Acapacitive insulating film 140 formed of a translucent insulating membersuch as silicon nitride is formed on the second interlayer insulatingfilm 138, to cover the common electrode 139.

The pixel electrodes 141 formed of a translucent conductive member suchas ITO are formed on the capacitive insulating film 140. Each pixelelectrode 141 is electrically coupled with the drain electrode 136 via acontact hole H extending through the capacitive insulating film 140, thesecond interlayer insulating film 138, and the first interlayerinsulating film 137. The common electrode 139 is provided with anopening portion corresponding to the formation region of the contacthole H and slightly larger than the contact hole H. The opening portionprovided in the common electrode 139 prevents the common electrode 139from contacting each pixel electrode 141. A first orientation film 148formed of polyimide or the like is formed on the capacitive insulatingfilm 140, to cover the pixel electrodes 141.

The second substrate 150 includes a second base material 151 formed of atranslucent insulating member such as glass. The color filters CF andthe black matrix BM are formed on an internal surface side (liquidcrystal layer 160 side) of the second base material 151. Each colorfilter CF is formed in a region (opening portion OBM) surrounded by theblack matrix BM. A second orientation film 152 formed of polyimide orthe like is formed on the color filters CF and the black matrix BM.

A first polarizing plate 149 is bonded to an external surface side (sidereverse to the liquid crystal layer 160) of the first base material 131.A second polarizing plate 153 is bonded to an external surface side(side reverse to the liquid crystal layer 160) of the second basematerial 151. A transmission axis of the first polarizing plate 149 is,for example, parallel with the Y direction. A transmission axis of thesecond polarizing plate 153 is, for example, orthogonal to thetransmission axis of the first polarizing plate 149. The firstorientation film 148 and the second orientation film 152 have beensubjected to orientation treatment by rubbing or ultraviolet irradiationor the like. Supposing that the direction in which orientation treatmentis performed is an orientation treatment direction AD (see FIG. 3), theorientation treatment direction AD of the first orientation film 148 is,for example, parallel with the X direction (second direction). Theorientation treatment direction of the second orientation film 152 is,for example, parallel with the orientation treatment direction AD of thefirst orientation film 148. The first orientation film 148 and thesecond orientation film 152 orient the liquid crystal layer 160 in the Xdirection.

The liquid crystal layer 160 includes liquid crystal molecules havingpositive dielectric anisotropy. The X direction (second directionorthogonal to the first direction) is the orientation direction of theliquid crystal molecules in an initial orientation state in which novoltage is applied between the pixel electrode 141 and the commonelectrode 139. When a voltage is applied between the pixel electrode 141and the common electrode 139, the liquid crystal molecules are orientedin the Y direction with an electric field formed between the pixelelectrode 141 and the common electrode 139. In the liquid crystaldisplay device 100, light and dark display is performed usingbirefringence based on difference in orientation state between theliquid crystal molecules as described above.

The following is specific explanation of the structure of the pixelelectrode 141 and movement of the liquid crystal molecules when avoltage is applied. FIG. 6 is an enlarged plan view of part of theelectrode structure illustrated in FIG. 5.

Each of the belt-like portions 142 includes a main line portion 142 aextending from one side (for example, +X side) to the other side (forexample, −X side) of the central line CL of the subpixel over thecentral line CL, a first extension portion 142 b 1 provided on one endside of the main line portion 142 a, and a second extension portion 142b 2 provided on the other end side of the main line portion 142 a. Eachof the belt-like portions 142 has a rotation-symmetrical shape withrespect to, for example, the center C of the belt-like portion 142.

The main line portion 142 a has a shape, for example, having a fixedwidth in the Y direction. In the present embodiment, the main lineportion 142 a has a parallelogram shape in which at least a portion (forexample, a portion disposed between the first coupling portion 143 a andthe second coupling portion 143 b) other than the longitudinal both endportions is inclined with respect to the X direction, but the shape ofthe main line portion is not limited thereto. For example, the main lineportion 142 a may have a rectangular shape in which at least the portionother than the longitudinal both end portions is parallel with the Xdirection.

Each of the first extension portion 142 b 1 and the second extensionportion 142 b 2 has, for example, a shape in which the width in the Ydirection is smaller in a position distant from the main line portion142 a. In each of the first extension portion 142 b 1 and the secondextension portion 142 b 2, two edges opposite to each other in the Ydirection are inclined in a direction approaching each other. In thepresent embodiment, each of the first extension portion 142 b 1 and thesecond extension portion 142 b 2 has a trapezoidal shape in which atleast a portion (for example, a portion disposed opposite to the centralline CL side of the coupling portion 143) other than an end portion onthe main line portion 142 a side is inclined with respect to the Xdirection, but the shape of the first extension portion 142 b 1 and thesecond extension portion 142 b 2 is not limited thereto. For example,the first extension portion 142 b 1 and the second extension portion 142b 2 may have a shape in which at least the portion other than the endportion on the main line portion 142 a side has a triangular shape.

The belt-like portions 142 include first belt-like portions 142A andsecond belt-like portions 142B that are mutually different in inclineddirection of the main line portion 142 a. The main line portion 142 a ofeach of the first belt-like portions 142A is inclined by an angle θ0(0<θ0<45°) counterclockwise with respect to the X direction. The mainline portion 142 a of each of the second belt-like portions 142B isinclined by an angle θ0 clockwise with respect to the X direction. Thefirst belt-like portions 142A and the second belt-like portions 142Bhave line-symmetrical shapes with respect to a line parallel with the Xdirection, for example.

The first belt-like portions 142A and the second belt-like portions 142Bare alternately arranged repeatedly in the Y direction, for example. Aspace (space between edges opposite to each other in the Y direction)between two adjacent belt-like portions 142 varies along the Xdirection. Two adjacent belt-like portions 142 are coupled with thecoupling portion 143 at a portion at which the space therebetween issmallest. In the example of FIG. 6, the coupling portion 143 is coupledto end portions of two main line portions 142 a approaching each other.The first coupling portions 143 a are disposed in a straight-line manneralong the Y direction, and the second coupling portions 143 b arearranged in a straight-line manner along the Y direction. The spacebetween two adjacent belt-like portions 142 increases as the distancethereof from the coupling portion 143 increases.

Each slit SL provided between two adjacent belt-like portions 142 isdivided by a corresponding coupling portion 143 of the plurality ofcoupling portions 143 into a first slit portion SL1 disposed closer tothe central line CL than the corresponding coupling portion 143 and asecond slit portion SL2 disposed further away from the central line CLthan the corresponding coupling portion 143. An edge of each belt-likeportion 142 facing the slit SL includes a first edge portion EG1 facingthe first slit portion SL1 and a second edge portion EG2 facing thesecond slit portion SL2. Each of the plurality of coupling portions 143includes a third edge portion EG3 facing the first slit portion SL1 anda fourth edge portion EG4 facing the second slit portion SL2.

An angle θ1 at which the first edge portion EG1 and the third edgeportion EG3 cross is an obtuse angle. An angle θ2 at which the secondedge portion EG2 and the fourth edge portion EG4 cross is an obtuseangle. The angle θ2 (a first angle) between the second edge portion EG2and the fourth edge portion EG4 is larger than the angle θ1 (a secondangle) between the first edge portion EG1 and the third edge portionEG3. In two adjacent belt-like portions 142, the space between the firstedge portions EG1 and the space between the second edges EG2 increase asthe distance thereof from the coupling portion 143 increases. Thisstructure enables easy stabilization of orientation of the liquidcrystal molecules in the first slit portion SL1 and the second slitportion SL2.

Each first edge portion EG1 includes a plurality of portions withmutually different inclination angles with respect to the third edgeportion EG3. The inclination angle (a first inclination angle) of aportion (a second portion) provided in a position distant from thecorresponding coupling portion 143 is larger than the inclination angle(a second inclination angle) of a portion (a first portion) provided ina position close to the corresponding coupling portion 143. A positionof the first portion is farther from the corresponding coupling portion143 than a position of the second portion. For example, in the firstedge portion EG1, an inclination angle θ3 of a portion corresponding tothe edge of the first extension portion 142 b 1 or the second extensionportion 142 b 2 is larger than the inclination angle θ1 of a portioncorresponding to the edge of the main line portion 142 a. This structureenables easy stabilization of orientation of the liquid crystalmolecules in a position distant from the coupling portion 143.

FIG. 7 is a diagram illustrating an orientation state of liquid crystalmolecules 160 a when a voltage is applied.

When a voltage is applied between the pixel electrode 141 and the commonelectrode 139 (see FIG. 5), the liquid crystal molecules 160 a in thevicinity of the edges opposite to each other of two adjacent belt-likeportions 142 are rotated in mutually opposite directions with respect tothe normal direction of the first substrate 130 (see FIG. 5). The liquidcrystal molecules 160 a (first liquid crystal molecules) in the vicinityof the first edge portion EG1 and the liquid crystal molecules 160 a(second liquid crystal molecules) in the vicinity of the second edgeportion EG2 that are adjacent in the X direction (second directionorthogonal to the first direction) with the corresponding couplingportion 143 interposed between the first edge portion EG1 and the secondedge portion EG2 are rotated in mutually opposite directions withrespect to the normal direction of the first substrate 130 (see FIG. 5).This structure achieves high-speed response.

In the operation, a plurality of line-shaped regions DL are formed ineach subpixel SPX. In the line-shaped regions DL, orientation of theliquid crystal molecules 160 a hardly changes, even when a voltage isapplied between the pixel electrode 141 and the common electrode 139(see FIG. 5). Specifically, a first line-shaped region DL1 extending inthe X direction and running through the center of the first slit portionSL1 is formed in a position superimposed on the first slit portion SL1.A second line-shaped region DL2 extending in the X direction and runningthrough the center of the second slit portion SL2 is formed in aposition superimposed on the second slit portion SL2. A thirdline-shaped region DL3 is formed in a position of a portion of thebelt-like portion 142 adjacent to the second slit portion SL2 in the Ydirection. A fourth line-shaped region DL4 is formed in the position ofthe coupling portion 143. The first line-shaped region DL1 and thesecond line-shaped region DL2 are line-shaped regions in which change inorientation of the liquid crystal molecules 160 a is limited byinterference between the liquid crystal molecules 160 a. The thirdline-shaped region DL3 and the fourth line-shaped region DL4 areline-shaped regions in which an electric field does not sufficiently acton the liquid crystal molecules 160 a and thereby orientation of theliquid crystal molecules 160 a does not easily change.

Display becomes dark in a portion in which a line-shaped region DL isformed. However, no line-shaped regions DL are formed in a portion(central portion of the belt-like portion 142) of the belt-like portion142 disposed between the first coupling portion 143 a and the secondcoupling portion 143 b. In the central portion of each belt-like portion142, because the liquid crystal molecules 160 a in the vicinity of theedge on the −Y side and the liquid crystal molecules 160 a in thevicinity of the edge on the +Y side are rotated in the same direction asviewed from the normal direction of the first substrate 130 (see FIG.5), orientation of the liquid crystal molecules 160 a provided in aposition superimposed on the belt-like portion 142 can be sufficientlychanged. With the structure, display is brightened in comparison withthe case where the line-shaped regions DL are formed in the wholebelt-like portion 142.

FIG. 8 is a plan view illustrating a transmission light image of thesubpixel SPX when a voltage is applied.

First line-shaped regions DL1 are formed at a first pitch W1 in a firstregion CA disposed in the central portion of the subpixel SPX in the Xdirection. Each of a second region SA1 positioned on a +X side of thefirst region CA and a third region SA2 positioned on a −X side of thefirst region CA is provided with the first line-shaped regions DL1,second line-shaped regions DL2, and third line-shaped regions DL3, at asecond pitch W2 shorter than the first pitch W1. The portions in whichthe first line-shaped regions DL1 and the second line-shaped regions DL2are formed are portions contributing to high-speed response. For thisreason, the second region SA1 and the third region SA2 more greatlycontribute to achievement of high-speed response than the first regionCA.

The sizes of the second region SA1 and the third region SA2 arecontrolled according to the positions of the coupling portions 143 (seeFIG. 7). The sizes of the second region SA1 and the third region SA2increase as the positions of the coupling portions 143 become closer tothe central line CL of the subpixel SPX. The sizes of the second regionSA1 and the third region SA2 decrease as the positions of the couplingportions 143 become more distant from the central line CL of thesubpixel SPX. Because the region contributing to high-speed responsedecreases as the sizes of the second region SA1 and the third region SA2decrease, the response speed decreases, but display is brightenedbecause the area occupied by the line-shaped regions DL is reduced. Bycontrast, because the region contributing to high-speed responseincreases as the sizes of the second region SA1 and the third region SA2increase, the response speed increases, but display is darkened becausethe area occupied by the line-shaped regions DL increases. Accordingly,the positions of the coupling portions 143 are properly designedaccording to the required response speed and brightness property.

In the second region SA1 and the third region SA2, because theline-shaped regions DL are densely formed, orientation of the liquidcrystal molecules more easily becomes unstable in comparison with thefirst region CA. For this reason, as illustrated in FIG. 6, the angle θ2at which the second edge portion EG2 and the fourth edge portion EG4cross is set larger than the angle θ1 at which the first edge portionEG1 and the third edge portion EG3 cross. This structure enablesorientation of the liquid crystal molecules in the vicinity of thesecond edge portion EG2 to be stabilized more easily than orientation ofthe liquid crystal molecules in the vicinity of the first edge portionEG1, and contributes to stabilization of the whole orientation of thesecond region SA2 and the third region SA3.

As described above, in the liquid crystal display device 100 accordingto the present embodiment, the coupling portions 143 coupling theadjacent belt-like portions 142 are arranged to be distributed to oneside and the other side of the central line CL with the central line CLof each subpixel SPX interposed therebetween. With the structure, noline-shaped regions DL are formed in positions on the belt-like portions142 provided between the first coupling portions 143 a disposed on oneside of the central line CL and the second coupling portions 143 bdisposed on the other side of the central line CL. This structureenables bright display.

Second Embodiment

FIG. 9 is a plan view illustrating an electrode structure of a liquidcrystal display device according to a second embodiment. In the presentembodiment, constituent elements that are the same as those in the firstembodiment are denoted by the same reference numerals, and detailedexplanation thereof is omitted.

The present embodiment is different from the first embodiment in thatthe first coupling portions 143 a couple end portions of two adjacentbelt-like portions 142. Each of the belt-like portions 142 includes nofirst extension portion 142 b 1 illustrated in FIG. 6. In the structure,neither second line-shaped region DL2 nor third line-shaped region DL3is formed on the +X side (side opposite to the central line side of thesubpixel) of the first coupling portion 143 a. This structure enablesbright display, although the response speed deteriorates, in comparisonwith the first embodiment.

Third Embodiment

FIG. 10 is a plan view illustrating an electrode structure of a liquidcrystal display device according to a third embodiment. In the presentembodiment, constituent elements that are the same as those in thesecond embodiment are denoted by the same reference numerals, anddetailed explanation thereof is omitted.

The present embodiment is different from the second embodiment in thatthe second coupling portions 143 b include a plurality of secondcoupling portions 143 b having mutually different positions in the Xdirection. The second coupling portions 143 b are not arranged in astraight-line manner along the Y direction. With the structure,positions of some of the second coupling portions 143 b arranged in theY direction are shifted in the X direction, to enable minute adjustmentof the brightness of display and the response speed.

Fourth Embodiment

FIG. 11 is a plan view illustrating an electrode structure of a liquidcrystal display device according to a fourth embodiment. In the presentembodiment, constituent elements that are the same as those in thesecond embodiment are denoted by the same reference numerals, anddetailed explanation thereof is omitted.

The present embodiment is different from the second embodiment in thateach of the second coupling portions 143 b couples end portions of twoadjacent belt-like portions 142. Each of the belt-like portions 142include neither the first extension portion 142 b 1 nor the secondextension portion 142 b 2 illustrated in FIG. 6. With the structure,neither line-shaped region DL2 nor third line-shaped region DL3 isformed on the +X side (side opposite to the central line side of thesubpixel) of the first coupling portion 143 a and the −X side (sideopposite to the central line side of the subpixel) of the secondcoupling portion 143 b. This structure enables bright display, althoughthe response speed deteriorates, in comparison with the secondembodiment.

Fifth Embodiment

FIG. 12 is a plan view illustrating an electrode structure of a liquidcrystal display device according to a fifth embodiment. In the presentembodiment, constituent elements that are the same as those in thefourth embodiment are denoted by the same reference numerals, anddetailed explanation thereof is omitted.

The present embodiment is different from the second embodiment in thateach main line portion 142 a is provided with a bent portion. An edge(first edge portion EG1) of each main line portion 142 a includes aplurality of portions (first portion EG11 and second portion EG12)having mutually different inclination angles with respect to the thirdedge portion EG3. An inclination angle α2 of the second portion EG12provided in a position distant from the coupling portion 143 is largerthan an inclination angle α1 of the first portion EG11 provided in aposition close to the coupling portion 143. This structure enables easystabilization of orientation of the liquid crystal molecules in theposition distant from the coupling portion 143.

Preferred embodiments of the present invention have been describedabove, but the present invention is not limited to the embodiments. Thedetails disclosed in the embodiments are mere examples, but can bevariously modified within a range not departing from the gist of thepresent invention. Proper modifications within the range not departingfrom the gist of the present invention also belong to the technicalscope of the present invention, as a matter of course.

For example, the embodiments described above illustrate the structure inwhich each pixel electrode 141 is disposed on the liquid crystal layer160 side of the common electrode 139 with the capacitive insulating film140 interposed therebetween, and the pixel electrode 141 is providedwith the belt-like portions 142 and the coupling portions 143, but thestructure of the pixel electrodes 141 and the common electrode 139 isnot limited thereto. For example, the common electrode 139 may bedisposed on the liquid crystal layer 160 side of the pixel electrode 141with the capacitive insulating film 140 interposed therebetween, and thecommon electrode 139 may be provided with the belt-like portions 142 andthe coupling portions 143.

In addition, the embodiments described above illustrate the structure inwhich the pixel electrodes 141 and the common electrode 139 are stackedwith the capacitive insulating film 140 interposed therebetween, but thestructure of the pixel electrodes 141 and the common electrode 139 isnot limited thereto. For example, the pixel electrodes 141 and thecommon electrode 139 may be formed adjacent to each other on the samelayer.

In the embodiments described above, the first coupling portions 143 aand the second coupling portions 143 b are alternately arranged in the Ydirection, but arrangement of the coupling portions 143 is not limitedthereto. For example, some of the first coupling portions 143 a may bearranged adjacent to each other in the Y direction. In the same manner,some of the second coupling portions 143 b may be arranged adjacent toeach other in the Y direction.

The layer structure of the first substrate 130 and the second substrate150 is a mere example, and is not limited to the structure of theembodiments described above. For example, FIG. 5 illustrates thestructure in which the color filters CF are provided on the secondsubstrate 150, but the color filters CF may be provided on the firstsubstrate 130. Specifically, the present invention may be applied to acolor filter on array (COA) structure.

In the specification, the description disclosing that the members havean equal size means that the sizes of the members are equal to eachother within a range of the manufacturing error. In the same manner, thedescription disclosing that the members are parallel or orthogonal toeach other means that the members are parallel or orthogonal to eachother within a range of the manufacturing error.

What is claimed is:
 1. A liquid crystal display device comprising: afirst substrate including a pixel electrode and a common electrode, asecond substrate disposed opposite to the first substrate; and a liquidcrystal layer disposed between the first substrate and the secondsubstrate, the liquid crystal layer including first liquid crystalmolecules and second liquid crystal molecules, wherein the pixelelectrode or the common electrode includes, in a single sub-pixel havinga first side area and a second side area that are divided by a centralline of the single sub-pixel, the central line extending in a firstdirection, a plurality of belt-like portions arranged in the firstdirection, and a plurality of coupling portions that are configured tocouple adjacent belt-like portions of the plurality of belt-likeportions, wherein each of the plurality of belt-like portionscontinuously extends from the first side area to the second side area ofthe single sub-pixel in a second direction that transverses the firstdirection, wherein the plurality of coupling portions includes one ormore first coupling portions provided in the first side area and one ormore second coupling portions provided in the second side area, whereina slit provided between two of the adjacent belt-like portions isdivided by a corresponding coupling portion of the plurality of couplingportions into a first slit portion disposed closer to the central linethan the corresponding coupling portion and a second slit portiondisposed further away from the central line than the correspondingcoupling portion, wherein an edge of a first belt-like portion of thetwo of the adjacent belt-like portions facing the slit includes a firstedge portion facing the first slit portion and a second edge portionfacing the second slit portion, and wherein the first liquid crystalmolecules that are close to the first edge portion and the second liquidcrystal molecules that are close to the second edge portion are rotatedin mutually opposite directions with respect to a normal direction ofthe first substrate, when a voltage is applied between the pixelelectrode and the common electrode.
 2. The liquid crystal display deviceaccording to claim 1, wherein the liquid crystal layer includes liquidcrystal molecules, and wherein, when the voltage is applied between thepixel electrode and the common electrode, the liquid crystal moleculesthat are close to edges opposite to each other of the two of theadjacent belt-like portions of the plurality of belt-like portions arerotated in mutually opposite directions with respect to the normaldirection of the first substrate.
 3. The liquid crystal display deviceaccording to claim 2, further comprising: a first orientation film,wherein the first substrate is provided with the first orientation filmthat orients the liquid crystal layer in the second direction.
 4. Theliquid crystal display device according to claim 1, wherein the one ormore first coupling portions and the one or more second couplingportions are alternately arranged repeatedly in the first direction. 5.The liquid crystal display device according to claim 1, wherein a spacebetween the two of the adjacent belt-like portions of the plurality ofbelt-like portions varies along the second direction, and the two of theadjacent belt-like portions are connected with the plurality of couplingportions at a portion at which the space between the two of the adjacentbelt-like portions is smallest.
 6. The liquid crystal display deviceaccording to claim 1, wherein, among the plurality of belt-like portionsprovided in the single sub-pixel, at least some of the plurality ofbelt-like portions provided in a central portion have a mutually equallength.
 7. The liquid crystal display device according to claim 1,wherein the liquid crystal layer includes liquid crystal moleculeshaving positive dielectric anisotropy, and an orientation direction ofthe liquid crystal molecules in an initial orientation state in whichthe voltage is not applied between the pixel electrode and the commonelectrode is the second direction.
 8. The liquid crystal display deviceaccording to claim 1, wherein the pixel electrode is disposed on aliquid crystal layer side of the common electrode with an insulatingfilm interposed between the pixel electrode and the common electrode,and the plurality of belt-like portions and the plurality of couplingportions are provided in the pixel electrode.
 9. The liquid crystaldisplay device according to claim 1, wherein a first edge length of thefirst edge portion is different from a second edge length of the secondedge portion.
 10. The liquid crystal display device according to claim1, wherein a first slit length of the first slit portion in the seconddirection is different from a second slit length of the second slitportion in the second direction.
 11. A liquid crystal display devicecomprising: a first substrate including a pixel electrode and a commonelectrode, a second substrate disposed opposite to the first substrate;and a liquid crystal layer disposed between the first substrate and thesecond substrate, wherein the pixel electrode or the common electrodeincludes, in a single sub-pixel having a first side area and a secondside area that are divided by a central line of the single sub-pixel,the central line extending in a first direction, a plurality ofbelt-like portions arranged in the first direction, and a plurality ofcoupling portions that are configured to couple adjacent belt-likeportions of the plurality of belt-like portions, wherein each of theplurality of belt-like portions continuously extends from the first sidearea to the second side area of the single sub-pixel in a seconddirection that transverses the first direction, wherein the plurality ofcoupling portions includes one or more first coupling portions providedin the first side area and one or more second coupling portions providedin the second side area, wherein a slit provided between two of theadjacent belt-like portions is divided by a corresponding couplingportion of the plurality of coupling portions into a first slit portiondisposed closer to the central line than the corresponding couplingportion and a second slit portion disposed further away from the centralline than the corresponding coupling portion, wherein an edge of a firstbelt-like portion of the two of the adjacent belt-like portions facingthe slit includes a first edge portion facing the first slit portion anda second edge portion facing the second slit portion, wherein thecorresponding coupling portion includes a third edge portion facing thefirst slit portion and a fourth edge portion facing the second slitportion, and wherein a first angle between the second edge portion andthe fourth edge portion is larger than a second angle between the firstedge portion and the third edge portion.
 12. The liquid crystal displaydevice according to claim 11, wherein a first edge length of the firstedge portion is different from a second edge length of the second edgeportion.
 13. The liquid crystal display device according to claim 11,wherein a first slit length of the first slit portion in the seconddirection is different from a second slit length of the second slitportion in the second direction.
 14. A liquid crystal display devicecomprising: a first substrate including a pixel electrode and a commonelectrode, a second substrate disposed opposite to the first substrate;and a liquid crystal layer disposed between the first substrate and thesecond substrate, wherein the pixel electrode or the common electrodeincludes, in a single sub-pixel having a first side area and a secondside area that are divided by a central line of the single sub-pixel,the central line extending in a first direction, a plurality ofbelt-like portions arranged in the first direction, and a plurality ofcoupling portions that are configured to couple adjacent belt-likeportions of the plurality of belt-like portions, wherein each of theplurality of belt-like portions continuously extends from the first sidearea to the second side area of the single sub-pixel in a seconddirection that transverses the first direction, wherein the plurality ofcoupling portions includes one or more first coupling portions providedin the first side area and one or more second coupling portions providedin the second side area, wherein a slit is provided between two of theadjacent belt-like portions coupled with a corresponding couplingportion of the plurality of coupling portions, wherein an edge of afirst belt-like portion of the two of the adjacent belt-like portionsfaces the slit, wherein the corresponding coupling portion includes acoupling edge portion facing the slit, wherein the edge of the firstbelt-like portion includes a first portion and a second portion thathave mutually different inclination angles with respect to the couplingedge portion, and wherein a first inclination angle of the secondportion is larger than a second inclination angle of the first portion,a position of the second portion being farther from the correspondingcoupling portion than a position of the first portion.